The invention relates generally to power transmission systems of the endless belt type and, more particularly, to such systems having powered and idler pulleys as components thereof
A typical endless-belt conveyor system has a head or driving pulley and a tail or idler pulley. Also typically, the axes of rotation of such pulleys are generally parallel to one another and horizontal, although neither parameter is an absolute requirement. An endless belt is mounted on and supported by such pulleys and, when viewed toward the belt edge, such belt defines what might be described as a very-elongate race track shape. The top portion of the belt is driven by the head pulley and is in tension. The lower portion may be somewhat slack.
Endless-belt conveyor systems are used for a wide variety of purposes. An example is a conveyor system moving granular or containerized products from one location to another. Another example, used in a commercial airport, moves passenger baggage from the baggage cart offloading area to the carousels at which passengers retrieve such baggage.
In conventional arrangements, a pulley (head or tail) has a one-piece shaft extending entirely through the pulley. Such shaft protrudes from either side by dimensions sufficient to mount the shaft ends on respective supporting bearings and (in the case of a powered head pulley) to apply driving torque to one end. An example of a type of conveyor having a narrow pulley and a through shaft is disclosed in U.S. Pat. No. 6,000,531 (Martin).
Like all mechanical structures, such conveyor systems experience failure, e.g., bearing failure, from time to time. And, often, the shaft supported by such bearing is damaged so as to require replacement. In a conventional system, the failure of a bearing requires that the pulley be entirely removed from the conveyor structure. This is so since the pulley shaft is a one-piece shaft. And it is highly desirable to leave the belt in place while effecting repairs. Often, the pulley is removed to another site for repair or substitution.
This is time consuming and runs the risk of damaging the pulley outer shell during handling. And when re-installed, the pulley outer shell, replacement shaft and other components must be precisely concentrically aligned or the pulley will xe2x80x9cwobblexe2x80x9d, result in undue belt wear and unduly stress the bearings.
And that is not all. A pulley is very heavy, difficult to handle and, therefore, difficult to re-align and mount following repair. If the conveyor system (including the failed pulley) is closely adjacent to another conveyor system (as is common in airport baggage handling arrangements) or to some other obstruction, the difficulty of repair is exacerbated. The system having the failed pulley (or the adjacent work-impeding structure) may have to be elevated with jacks in order to get at and remove the affected pulley, shaft and bearing.
An improved conveyor roller which addresses problems of known pulleys would be an important advance in the art.
It is an object of the invention to provide a conveyor pulley overcoming some of the problems and shortcomings of prior art pulleys.
Another object of the invention is to provide a conveyor pulley which is easy to replace.
Another object of the invention is to provide a conveyor pulley configured to permit bearing or shaft replacement while yet avoiding removal of the pulley from the conveyor system.
Still another object of the invention is to provide a conveyor pulley which is less costly to repair that known pulleys.
Yet another object of the invention is to provide a conveyor pulley which may be readily serviced, notwithstanding the proximity of other equipment or of an obstruction.
Another object of the invention is to provide a conveyor pulley which, when compared to a similar prior art pulley, is lighter in weight. How these and other objects are accomplished will become apparent from the following descriptions and the drawings.
The new conveyor pulley is configured to revolve about an axis of rotation. Such pulley includes a cylindrical drum or shell and first and second bushing portions supported within the shell. A first shaft portion is in torque-transmitting engagement with the first bushing portion; and a second shaft portion is in torque-transmitting engagement with the second bushing portion.
The first and second shaft portions are restrained from axial movement with respect to the first and second bushing portions, respectively. In a specific embodiment, such restraint is provided by fasteners coupling a shaft portion and its respective bushing portion to one another. The first and second shaft portions are spaced from one another, that is, such shaft portions are separate components independently replaceable.
In a highly preferred embodiment, the first shaft portion includes a flange (a xe2x80x9cfirstxe2x80x9d flange) which might be described as xe2x80x9crace track shapedxe2x80x9d. Such flange has a pair of arcuate ends (of the same radius of curvature) which are joined by a pair of linear sides. The first bushing portion includes a xe2x80x9cfirstxe2x80x9d face and the first shaft portion is restrained by at least one fastenerxe2x80x94a xe2x80x9cfirstxe2x80x9d fastenerxe2x80x94and, preferably, by plural fasteners such as cap screws which engage the flange and the face.
In other aspects of the inventive pulley, the first bushing portion includes a groove having at least one linear edge and extending along a groove axis. Such axis is generally perpendicular to the axis of rotation. The flange is received in the groove and bears against the edge. Considered another way, the groove and the flange are conformably shaped and sized in such a way that the flange may be fitted into the groove with closely-fitted sliding clearance so as to avoid rotational xe2x80x9cplayxe2x80x9d between the shaft portion and bushing portion. The first bushing portion and first shaft portion are at one end of the pulley, the other end is similarly configured in that such end is substantially a xe2x80x9cmirror imagexe2x80x9d of the first end.
More specifically, the second bushing portion includes a second face, the second shaft portion includes a second flange and the second shaft portion is restrained by at least a second fastener engaging the second flange and the second face. Most preferably, the second shaft portion and the second bushing portion are secured to one another by plural fasteners.
In other aspects of the inventive pulley, a first support structure is interposed between the shell and the first bushing portion. Similarly, a second support structure interposed between the shell and the second bushing portion. Such support structures retain, respectively, the first and second bushing portions in fixed positions with respect to the shell. While such support structures may be configured as xe2x80x9cspidersxe2x80x9d, support rods or the like, in a highly preferred embodiment, the first and second support structures include, respectively, annular members. Each annular member is affixed to the shell and to its respective bushing portion by welding, for example. Most preferably, each support structure comprises a pair of spaced-apart annular webs affixed to the shell and respective bushing portions. A preferred web is xe2x80x9cwasher likexe2x80x9d and disc-shaped.
While it is preferred to construct the new pulley with two spaced-apart bushing portions (as separate pieces secured within the pulley shell), that is not the only way to construct an operative pulley although it may be the lowest-cost configuration consistent with the required rigidity, xe2x80x9crobustnessxe2x80x9d and the like. In an alternate embodiment, the pulley includes a single bushing tube extending along the pulley axis of rotation. Such tube has first and second ends, the first shaft portion terminates at the first end and the second shaft portion terminates at the second end.
In the embodiments described, the shell, shaft portions and bushing portions are all concentric with the pulley axis of rotation. The shaft portions are independently removable from their respective bushing portions and, most preferably, a particular shaft portion and its mating bushing portion are in torque-transmitting engagement with one another. Even if shaft portions were configured to have a length causing such portions to actually touch one another inside the shell, this is not the preferred arrangement. Such shaft portions are considered to be xe2x80x9cspacedxe2x80x9d from one another, even if only minutely, and of course would be independently removable, a feature of the invention.
Other aspects of the invention involve a method for repairing a conveyor structure. Such structure has a driven or head pulley and an idler or tail pulley. Each pulley includes first and second stub shafts axially spaced from one another and supported by first and second bearings, respectively. It is assumed that one of the pulleys has failed by, e.g., having one of the bearing seize. With such a seizure, there is a high likelihood that the shaft portion supported by such bearing is also damaged and should be replaced.
The method includes the steps of determining that the failure is associated with, for example, the first shaft and the first bearing of the head pulley. The first bearing is detached from the structure and the head pulley first stub shaft is removed therefrom. A new stub shaft and/or new first bearing are attached and/or mounted, the new stub shaft being installed in place of the first stub shaft. The structure is then re-assembled.
A typical conveyor structure includes a pair of spaced-apart frame members. When the conveyor is operating, the pulleys are supported between the frame members (i.e., laterally between such members or somewhat above but yet between them). In a highly preferred method, the detaching step is carried out while supporting the head pulley between the frame members. Similarly, the removing step is carried out while supporting the head pulley between the frame members.
In the alternative, it is assumed that the failure is associated with the first shaft and the first bearing of the tail pulley. The tail pulley first bearing is detached from the structure; the tail pulley first stub shaft is removed from the tail pulley and a new stub shaft is attached in place of the first stub shaft of the tail pulley. Then the structure is re-assembled.
As with a failure associated with the head pulley, the detaching step is carried out while supporting the tail pulley between the frame members. And, most preferably, the removing step is also carried out while supporting the tail pulley between the frame members.
From the foregoing and from the detailed description which follows, advantages of the new pulley will be apparent. One no longer need remove the entire pulley to another location to effect repair. Such repair can be carried out while simply supporting the affected pulley substantially xe2x80x9cin placexe2x80x9d and replacing bearing(s) and/or shaft portion(s) as needed.